Process for recovering lithium values



United States atent PROCESS FOR RECOVERING LITHIUM VALUES John A.Peterson, Arlington Heights, 111., assignor to International Minerals &Chemical Corporation, a corporation'of New York No Drawing. ApplicationMarch 28, 1957 Serial No. 649,006

8 Claims. (CI. 23-27) This invention relates to the recovery of lithiumvalues from lithium-bearing ores and is particularly directed to aprocess for recovering lithium values from spodumene.

Various methods have been utilized in the past for recovering lithiumvalues from lithium-bearing ores. According to one procedure, the ore istotally or partially decomposed with an acid, such as sulfuric acid orfluo- .silicic acid. According to another procedure, an ore is fused orsintered with an inorganic compound, for

.example calcium sulfate, calcium chloride, calcium carbonate, orcalcium oxide, or a mixture thereof, and the lithium salts are extractedfrom the fusion products by means of mineral acids. Another methodinvolves base-exchange techniques, in which lithium ions are replaced inthe ore lattice by alkali-metal ions or hydrogen ions. This procedure iscarried out by treating an ore with a molten alkali sulfate or chlorideor an aqueous solution of such a salt at elevated temperature undersuperatmospheric pressure. Still another method involves conversion ofthe lithium compounds in the ore to lithium chloride, followed byvolatilization of the lithium chloride at high temperature.

The methods used in the past for recovering lithium values fromlithium-bearing ores generally have the serious disadvantage that theyremove from the ore relatively large quantitiesof impurities which maytake the form of aluminum or iron salts or similar materials. Manyprocesses heretofore utilized also have been expensive and/ orcumbersome to operate.

An object of this invention is to provide a simple and efficient processfor recovering lithium values from lithium-bearing ores, in particularfrom spodumene.

Another object is to provide a process for treating spodumene andrecovering lithium values therefrom substantially entirely free fromimpurities.

Another object is to provide a method for treating spodumene at elevatedtemperature and converting the lithium values therein into soluble form,while avoiding sintering and fusion of the reaction mixture.

Another object is to provide a method for heat-treating spodumene in arotary kiln and converting the lithium values therein into soluble form,while avoiding fusion and ringing within the kiln.

The present invention is an improvement upon the invention described andclaimed in my co-pending application, Serial No. 448,743, filed August9, 1954, now

abandoned, of which the present application is a continuation-in-part.In said earlier invention, calcined spodumene is reacted with theacetate or formate salt of sodium or potassium at a temperature abovethe melting point of said salt. The lithium values are converted therebyinto soluble form, and are readily leached from the treated ore withwater.

In the present invention, sodium carbonate or potassium carbonate isincorporated in the calcination mixture of my earlier process. Forexample, beta-spodumene is commingled with sodium formate and sodiumcarbonate and heated to the fusion temperature of sodium formate. Theextent of lithium recovery can be materially improved in this way, andin addition the tendency of the reaction mixture to soften or fuse islargely eliminated, so that caking, ringing, and clogging do not occurin the reaction vessel.

My invention thus comprises calcining beta-spodumene in admixture with asalt selected from the group consisting of sodium formate, sodiumacetate, potassium formate, and potassium acetate, and another saltselected from the group consisting of sodium carbonate and potassiumcarbonate. Mixtures of salts may also be employed if desired, e.g. amixture of sodium formate, acetate, and carbonate, or a mixture of thecorresponding potassium salts, or a mixture of sodium and potassiumsalts of the defined groups. Distinctly superior results are obtained,however, from a mixture of sodium formate and sodium carbonate, as wellas from a mixture of potassium formate and potassium carbonate.

In accordance with my invention, a sutficient quantity of sodium orpotassium carbonate is incorporated in the reaction mixture to providebetween about one-sixth and about five-sixths of the total alkali metalin the reaction mixture, preferably between about one-third and abouttwo-thirds. The presence of sodium or potassium carbonate in thereaction mixture during the reaction results in higher recoveries oflithium values from the spodumene than is possible in the completeabsence of said carbonates, while at the same time allowing for economywith respect to the amount of lower organic acid salt required. Sodiumor potassium carbonate may be utilized to reduce the quantity of lowerorganic acid salt required by as much as about In carrying out theprocess of the invention, spodumene ore is heated at about 1000" C. forabout one hour to convert the alpha-spodumene therein intobeta-spodumene, which reacts more rapidly and completely in thesucceeding steps of the process. The calcined material is comminuted, ifnecessary, and comminged with sodium formate and sodium carbonate orother salts as set forth hereinabove. It is desirable that the materialsbe in intimate contact, and this can be furthered by pelletizing themixture. The combined materials are then heated to a temperature at orabove the melting point of the organic salt in its anhydrous form, andpreferably to a temperature above about 200 C. in any case, for a timesufficient to permit the reaction to go to completion, that is, untilsubstantially all of the lithium ions in the spodumene have beenreplaced by alkali metal ions from the salts that were commingledtherewith. The temperature should not, of course, exceed the level atwhich substantial decomposition of the organic salt occurs. The reactiontemperature and time required in any given instance will vary dependingupon the particular salts utilized, the purity of the spodumene beingtreated, the degree of contact between the salts and the spodumene, theparticle size of the spodumene, and related factors. When the organicsalt is sodium formate, the reaction is suitably carried out at atemperature above 253 C. and preferably at a temperature between about270 and about 300 C. for a period of about 30 minutes to about 1.5hours. When sodium acetate is employed, the preferred temperature rangeis between about 335 and about 350 C. for a period of at least 5 minutesand preferably from about 10 minutes to about 1.5 hours. The reactiongenerally may be carried out in less than about 2 hours and in someinstances in as short a time as 5 minutes. Usually the reaction timewillbe from about 10 minutes to about 1.5 hours, when the spodumene is of afineness of less than 50 mesh. It is always desirable to carry out thereaction at a temperature above the melting point of the sodium orpotassulting in lessened efficiency. At temperatures lower than themelting point of the salt, rates of reaction are slow and attainment ofintimate contact between the salt and ore is difficult. At higherreaction temperatures the time required to complete the reaction will becorrespondingly reduced.

Following completion of the reaction, the reaction product is treatedwith water to leach the water-soluble lithium values from the ore and tosecure a solution containing lithium carbonate and lithium formate oracetate, depending upon which organic-acid salt was used in the heattreatment, together with sodium and/or potassium salts. The lithiumvalues can be conveniently recovered therefrom by evaporation, wherebythe comparatively insoluble lithium carbonate is precipitated and can befiltered oil. Additional sodium carbonate or potassium carbonate can beintroduced into the solution, if necessary, preferably beforeevaporation, to efiect substantially complete precipitation of thelithium values.

The liquor remaining after separation of the lithium carbonate containsformate and/or acetate of sodium and/or potassium, together with anyexcess carbonate and ordinarily a small quantity of unprecipitatedlithium. These values are readily recovered by evaporating the liquor toa thick slurry and recycling to treat a further quantity of spodumene.The water content of such a slurry serves as a pelleting aid for the newreaction mixture. Alternatively, the evaporation of the liquor can becarried to the point of yielding a solid, which can be driediii-desired, eomminuted, and recycled.

By means of the process of this invention, substantially all of thelithium values can be recovered without the attendant removal of anysubstantial amounts of silica, aluminum, iron, or other impurities.

The minimum quantity of sodium or potassium ions required to effectsubstantially complete recovery of the lithium is the quantity which istheoretically necessary to replace all of the lithium values in thestarting material. The total quantity of sodium or potassium provided bythe alkali metal carbonate and lower organic acid salt during thereaction should amount to at least about one atom per atom of lithium inthe beta-spodumene being treated, and preferably between about 2.5 andabout 3.5 atoms for each atom of lithium. Greater quantities of sodiumor potassium may be used if desired; such quantities, however, simplyadd to the expense of the process. H

The following examples illustrate specific embodiments of thisinvention. All parts and percentages are by weight unless otherwiseindicated.

Example 1 Alpha-spodumene containing 3.44% lithium was heated at about1100 C. for about 1 hour to effect transition to the beta-spodumeneform. About 100 parts of the beta-spodumene were comminuted until 100%would pass through a 100 mesh screen, then intimately mixed with 33.8parts of sodium formate and 52.4 parts of sodium carbonate andpelletized, utilizing about 8 parts of water. The pellets were heatedfor about 1 hour at about 290 C., at which temperature they retainedtheir original shape. The hot pellets were quenched in about 1380 partsof water, and were disintegrated thereby. The slurry thus formed wasagitated for one-half hour to dissolve soluble lithium values from thesolid material in the slurry. The slurry was then filtered and thefiltrate analyzed for lithium. It was found that the filtrate contained87% of the lithium originally present in the ore. The filtrate wasevaporated to about 90 parts to precipitate the lithium as lithiumcarbonate. The resulting slurry was heated to about 100 C. andimmediately filtered to remove the lithium carbonate product..

The product weighed 15.6 parts and comprised 99% lithium carbonate.

The lithium carbonate mother liquor was readily proc-- essed to recoverthe formate,- carbonate, and lithium values therein. The liquor wasevaporated to a dry solid weighing 60 parts and containing 75% (25.4parts) of the input sodium formate, 66%, (34.5 parts) of the inputsodium carbonate, and 3.2% (0.11 part) of the input lithium. This wascomminuted and recycled to treat a further quantity of beta-spodumene.

Example 2 Beta-spodumene prepared as in Example 1 and containing 3.44%lithium was added in the amount of about parts to 40.8 parts of sodiumacetate and 52.4 parts of sodium carbonate, and the mixture wasintimately commingled and pelletized using about 8 parts of water. Thepellets were heated for about 1 hour at 344 C. and extracted with about1380 parts of Water. Analysis of the aqueous extract liquor showed that81.5% o'f'the lithium values originally present in the ore had beenextracted. The lithium values were recovered from the solution aslithiumcarbonate following the procedure of Example 1.

Example A series of tests were carried out onthe beta-spodumene ofExample 1, following the procedure described therein, in which the ratioof sodium formate to sodium carbonate was varied, while the atomic ratioof total sodium to lithium was held constant at 3:1 in all of the tests.The results show a pronounced maximum in lithium recovery at afo'rrn'ate to carbonate molar ratio between about 2:1 and 11:2,

Na: Li Atomic Ratio Lithium Extracted, As As percent Formats CarbonateExample 4 Na: Li Atomic Ratio Lithium Extracted,

As As percent Acetate Carbonate The foregoing examples are intendedonlyas illustrations of my invention and not as a measure of the scopethereof. Numerous modifications and equivalents of the invention will beapparent from the present description to those skilled in the art.

In accordance with the foregoing description, I claim as my invention:

1. A process for recovering lithium values from betaspodumene whichcomprises commingling beta-spodumene, an organic alkali-metal saltselected from the group consisting of the sodium and potassium salts offormic and acetic acids, and an inorganic alkali-metal salt selectedfrom the group consisting of sodium carbonate and potassium carbonate,the total quantity of said salts being sufficient to provide an atomicratio of the alkali metal therein to the lithium in the beta-spodumeneof at least 1, and the quantity of said carbonate salt being at leastabout one-sixth of the total quantity of said salts, heating theresulting mixture at a temperature intermediate the melting point ofsaid organic salt in its anhydrous form and the temperature at whichsubstantial decomposition of said organic salt occurs for a timesufiicient to convert the lithium values in said beta-spodumene intowatersoluble form, and dissolving the lithium values therefrom withwater.

2. The process of claim 1 wherein said alkali-metal salts are employedin an amount sufiicient to provide an atomic ratio of alkali metaltherein to the lithium in the 'beta-spodumene between about 2.5 andabout 3.

3. The process of claim 1 in which between about onesixth and aboutfivxe-sixths of the total alkali metal is in the form of said inorganicsalt.

4. The process of claim 1 in which between about onethird and abouttwo-thirds of the total alkali metal is in the form of said inorganicsalt.

5. The process of claim 1 wherein said alkali-metal salts are sodiumsalts. Y

6. The process of claim 1 wherein said alkali-metal salts are potassiumsalts.

7. A process for recovering lithium values from betaspodumene whichcomprises commingling beta-spodumene with sodium formate and sodiumcarbonate in a proportion to produce an atomic ratio of sodium to thelithium in the beta-spodumene of at least 1, between about one-third andabout two-thirds of the quantity of added sodium being in the form ofsodium carbonate, heating the resulting mixture at a temperature aboveabout 253 C. and below the temperature at which anhydrous sodium formatesubstantially decomposes for a time sufiicient to convert the lithiumvalues in said beta-spodumene into water-soluble form, and leaching thelithium values therefrom with water.

8. A process for recovering lithium values from betaspodumene whichcomprises commingling beta-spodumene with sodium acetate and sodiumcarbonate in a proportion to produce an atomic ratio of sodium to thelithium in the beta-spodumene of at least 1, between about one-third andabout two-thirds of the quantity of added sodium being in the form ofsodium carbonate, heating the resulting mixture at a temperature aboveabout 320 C. and below the temperature at which anhydrous sodium acetatesubstantially decomposes for a. time sulncient to convert the lithiumvalues in said beta-spodumene into water-soluble form, and leaching thelithium values therefrom with water.

References Cited in the file of this patent UNITED STATES PATENTS2,021,986 Colton Nov. 26, 1935 2,230,167 Sivander et a1. Jan. 28, 19412,662,809 Kroll Dec. 15, 1953 2,816,007 Kroll Dec. 10, 1957

1. A PROCESS FOR RECOVERING LITHIUM VALVUES FROM BETASPODUMENE WHICHCOMPRISES COMMINGLING BETA-SPOUDUMENE, AN ORGANIC ALKALI-METAL SALTSELECTED FROM THE GROUP CONSISTING OF THE SODIUM AND POTASSIUM SALTS OFFORMIC AND ACETIC ACIDS, AND AN INORGANIC ALKALI-METAL SALT SELECTEDFROM THE GROUP CONSISTING OF SODIUM CARBONATE AND POTASSIUM CARBONATE,THE TOTAL QUANTITY OF SAID SALTS BEING SUFFICIENT TO PROVIDE AN ATOMICRATIO OF THE ALKALI METAL THEREIN TO THE LITHIUM IN THE BETA-SPODUMENEOF AT LEAST 1, AND THE QUANTITY OF SAID CARBONATE SALT BEING AT LEASTABOUT ONE-SIXTH OF THE TOTAL QUANTITY OF SAID SALTS, HEATING THERESULTING MIXTURE AT A TEMPERATURE INTERMEDIATE THE MELTING POINT OFSAID ORGANIC SALT IN ITS ANHYDROUS FROM AND THE TEMPERATURE AT WHICHSUBSTANTIAL DECOMPOSITION OF SAID ORGANIC SALT OCCURS FOR A TIMESUFFICIENT TO CONVERT THE LITHIUM VALVES IN SAID BETA-SPODUMENE INTOWATERSOLUBLE FROM, AND DISSOLVING THE LITHIUM VALVES THEREFROM WITHWATER.